European Patent Application Publication Number 0 475 213 A1 published 18.03.92 Bulletin 92/12 (hereinafter "The EP Application") based on U.S. Patent Applications Ser. Nos. 578,697 filed Sep. 4, 1990; 578,696 filed Sep. 4, 1990, and 686,956 filed Apr. 18, 1991, teaches a glazing unit having an edge assembly having low thermal conductivity and a method of making same. In general, The EP Application teaches an insulating unit having a pair of glass sheets about an edge assembly to provide a compartment between the sheets. The edge assembly has a U-shaped spacer that is moisture and/or gas impervious, and has materials selected and sized to provide the edge assembly with a predetermined RES-value (as defined and determined in the disclosure of The EF Application). The EP Application further discloses a triple glazed unit having a low thermal conducting edge.
U. S. Pat. No. 4,149,348 teaches a technique for making a triple glazed unit. In general, the triple glazed unit includes a pair of outer glass sheets separated by a spacer-dehydrator element, or metal spacer, having a groove to maintain a third glass sheet between the outer two glass sheets.
Although the triple glazed unit taught in U.S. Pat. No. 4,149,348 is acceptable, there are limitations. More particularly, the spacer-dehydrator element is structurally stable and is formed with a groove prior to its use. The spacer has desiccant therein; therefore, it is stored in a dry environment to prevent adsorption of moisture by the desiccant. The metal spacer has to be formed to have a groove; the additional forming increases the fabrication cost of the spacer. Further, the groove formed in the spacer disclosed is U.S. Pat. No. 4,149,348 maintains the third glass sheet spaced from the outer sheets; therefore, the groove has to be properly sized to prevent movement of the inner sheet relative to the outer sheets.
As can be appreciated, it would be advantageous to provide an insulating unit having three or more sheets that does not require storage of prefabricated materials e.g. a spacer-dehydrator element having a groove, does not require shaping the spacer to have a groove, and does not depend solely on the groove formed in the spacer to secure the intermediate sheet in position.